Closed Circuit Television, more commonly referred to as the CCTV system is widely known and used for surveillance, management and for different types of transportation. In most recent development, CCTV systems are being installed in department stores, banks, exhibition centers as well as surrounding area near the schools and residential areas among others for securing safe environment against crime. The outlook predicts that CCTV system will be even more widespread in the near future.
CCD cameras are frequently used in CCTV system in order to take picture of the images.
It is to be noted that CCD is the abbreviation for solid state image sensor wherein photoelectric conversion sensor with the size of 6 mm by 4 mm that has the photoelectric part that changes the light into electric signal and the transmission part that sends the charged electricity that was stored after the conversion.
Basic principle of the conversion sensor is that the light intensity is first recorded in CCD which operates in the same way that the film does in optic camera. Simultaneously, photographed light will be divided into different colors by the RGB filter attached to CCD.
After this, colors that are divided change into electric signals from thousands of light sensor that form the CCD. Analog signal from the CCD is converted to digital signal of either 0 or 1, thus creating a video signal and manifested on the screen. In case of digital camera with 41 thousand pixels, there are 41 thousand light sensors per one CCD.
However, early CCD cameras didn't have zoom function that controls the magnification of the lens unlike the regular optics camera. This caused inconvenience in the sense that the early CCD cameras could only photograph images with fixed ratio.
Most of the latest CCD cameras in the market have zoom and focusing functions and number of other related patented technologies as well.
To provide specific examples of technologies as mentioned above, regulating ring is rotated from the back of camera housing which in turn controls the gear, lens focus and gear in the zoom area as the spur gear type, regulating ring is rotated from top of the camera housing which in turn controls the gear, lens focus and gear in the zoom area as the helical gear type, controlling the lens focus and zoom by rotating the housing on side of the housing where the housing is disassembled without the gear to assemble the lens part, and adjusting the focus and zoom by using the motor through the method of installing the motor in the housing.
However, this type of structure has various drawbacks and limitations in manufacturing and installation process as it makes the size of the CCTV camera bigger. 6 millimeter sized CCD cameras that have auto-focusing function came out in the market. In case of board camera, 4 millimeter sized CCD cameras are used as well.
There is a disadvantage in the sense that the structure and the control becomes complicated as one motor processes both auto focusing and zoom function in order to make the CCD cameras smaller. Not only this, but it also takes longer time to process and focusing function failing to work in certain zoom ratio. When one motor is used, units for zoom and focusing function has to be set manually when one motor is used as it becomes more difficult, complicated, hard to control and takes longer time to process.
Moreover, signal processing function in pre-existing CCTV has to convert back and forth from analog signal and digital signal through one channel which causes overload when processing user interface and video signal and increase of memory that makes it difficult for effective control.
In addition, errors that occur regarding autofocus function cannot be fixed nor verified in pre-existing CCTV wherein it is considered as a limitation.